Find the slope for the pair of points (1,1)(4,-4)

(1, 1) and (4, -4)

Slope formula is : m = (y₂-y₁) / (x₂-x₁)

In this case :

x₁ = 1 ; x₂ = 4 ; y₁ = 1 ; y₂ = -4

Now that you know what variable counts as what, we simply just need to plug everything in.

m = (-4 - 1) / (4 - 1)

Simplify.

m = -5/3

Therefore, your slope is -5/3

~Hope I helped~ :)

Yes, two vertical lines can be complementary